1. Field of the Invention
The present invention relates to a dual clutch transmission to be equipped on a vehicle, the dual clutch transmission comprising: a first clutch to be engaged for activating each of odd-numbered speed drive trains for setting respective odd-numbered speeds; and a second clutch to be engaged for activating each of even-numbered speed drive trains for setting respective even-numbered speeds.
2. Related Art
As disclosed in JP 2007-218277, there is a well-known conventional dual clutch transmission which receives power from a prime mover and is automatically gearshifted to change the speed of the output rotation thereof to be transmitted to an axle of a vehicle. The dual clutch transmission comprises a group of odd-numbered speed gear trains, a group of even-numbered speed gear trains, a first clutch, and a second clutch. When one of the odd-numbered speed gear trains is selected to be activated, the selected odd-numbered speed gear train is activated by engaging the first clutch, i.e., receives power from the prime mover through the engaged first clutch. When one of the even-numbered speed gear trains is selected to be activated, the selected even-numbered speed gear train is activated by engaging the second clutch, i.e., receives power from the prime mover through the engaged second clutch.
During the gearshift of the dual transmission between odd and even numbered speeds, a next speed gear train is selected while a current speed gear train still remains engaged, i.e., the current speed gear train and the next speed gear train are simultaneously selected to be driven, and then one of the first and second clutches having been engaged for activating the current speed gear train is disengaged while the other of the first and second clutches is engaged so as to activate the next speed gear train, i.e., the engagement and disengagement of the first and second clutches overlap, thereby ensuring gearshift without intermittence of power transmission.
Further, in the above reference, a reverser clutch unit including a forward traveling clutch and a backward traveling clutch is provided downstream of the dual clutch transmission, so as to select whether the output rotation of the dual clutch transmission in the direction for forward traveling or backward traveling. However, the addition of the reverser clutch unit to the first and second clutches of the dual clutch transmission means increase of the number of expensive clutches.
Further, even if a working vehicle equipped with the dual clutch transmission has to be used for a work, such as a loading-and-unloading work or a cultivating work, requiring frequent reversing of forward/backward traveling direction, the gearshift of the conventional dual clutch transmission for reversing the traveling direction takes a long time which spoils the workability and requires this vehicle to travel a long distance because the forward traveling speed is gradually shifted down one speed by one speed to the neutral state before realizing the backward traveling speed. Further, the reverser clutch unit must have a power transmission torque for receiving the output power from the dual clutch transmission, thereby increasing the capacity thereof and costs.
Then, the alternate and overlapping engagement/disengagement function of the first and second clutches of the dual clutch transmission is desired to be utilized for such a work requiring frequent reversing of forward/backward traveling direction, so as to realize the half-clutch state of the first and second clutches during the forward/backward traveling direction shift, thereby requiring no shift down of speed to the neutral state. Here, if the vehicle is an agricultural tractor or the like, the dual clutch transmission of the vehicle is configured to provide many forward traveling speeds, and therefore, a plurality of backward traveling speeds are desired to be provided in correspondence to the many forward traveling speeds.